<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="utf-8">
	<title></title>
	<style type="text/css">
		.box{
			width: 200px;
			height: 200px;
			background-color: gold;
			/* auto 使盒子居住 */
			/* margin: 50px auto 100px auto; */
			margin: 50px auto 100px;	
		}

	</style>
</head>
<body>
	<div class="box"></div>

</body>
</html>